The continent used to be called Australia, but because Australia was the name of a country, it was changed to Oceania to suit NZ and the islands in the South Pacific. The name was changed ~10 years ago, so most people wouldn't have learned it in school.
The metric system is not so good at this, but it is easier to remember and has much more scientific utility as different types of measurements can easily be translated into each other.
For example, 1C is the temperature rise when 1 cc of water is heated by 1 joule of energy (under normal atmospheric pressure). Or something like that... someone can correct me on however I got that wrong
The point is, Oceania is clear as a hint, you should just work with it ;) If it said Australia instead, what should it say for Auckland?
Btw, as far as I'm concerned, there are only two continents: Afro-Eurasia and America. You either live on a continent, or on an island. The latter includes people living the UK, Indonesia and Japan.
As for the comment about the name "America", it was called that (singular) way before some countries divided it in two and started using the plural, probably to distinguish it from the US, which is incorrectly called "America".
In Switzerland, you basically never refer to a city by naming the agglomeration figure, but even including this weird counting system of citypopulation.de, which basically includes everything within 20 km, regardless of the landscape, Bern still doesn't reach 500k.
Geneva Town population is 198,979
Bern Town population is 133'315
All are less than the 500'000 minimum limit you mentioned !
Is it because it is part of the US? Well I guess French Guyana is part of Europe then.